H.A. Snyman

The influence of water stress on non-structural carbohydrate concentration in Themeda triandra

The objective of this study was to determine the influence of four different watering treatments (T1 = 75-100%, T2 = 50-75%, T3 = 25-50% and T4= 0-25% of Field Water Capacity) on the concentration of total non-structural carbohydrates during three growth stages (vegetative, pipe and reproductive) and also in three plant parts (roots, stubble and leaves) of the indigenous C4 grass species Themeda triandra. The total non-structural carbohydrate concentration (TNCC) was higher in all the plant parts (P≤0.05) as well as all the growth stages (P≤0.05), in T4 than T1. The results confirm that total non-structural carbohydrates are allocated (as growth reserves) to certain plant parts with increased water stress, with the largest allocation to the stubble. Because a mid-summer drought is more the rule than the exception in semi-arid areas, severe defoliation of Themeda triandra in the pipe growth stage during these conditions will be extremely detrimental to the survival of this key forage plant.